1. Field
The present application relates generally to the operation of communication systems, and more particularly, to methods and apparatus for noise estimation in a communication system.
2. Background
Data networks, such as wireless communication networks, have to trade off between services customized for a single terminal and services provided to a large number of terminals. For example, the distribution of multimedia content to a large number of resource limited portable devices (subscribers) is a complicated problem. Therefore, it is very important for network administrators, content retailers, and service providers to have a way to distribute content and/or other network services in a fast and efficient manner and in such a way as to increase bandwidth utilization and power efficiency.
In current content delivery/media distribution systems, real time and non real time services are packed into a transmission frame and delivered to devices on a network. For example, a communication network may utilize Orthogonal Frequency Division Multiplexing (OFDM) to provide communications between a network server and one or more mobile devices. This technology provides a plurality of subcarriers that are modulated with data representing services to be delivered over a distribution network as a transmit waveform. Thus, the ability to receive and accurately process the transmit waveform determines how well the system will perform.
The signal to interference/noise ratio (SINR) is one of the most important parameters that characterize the signal quality and the receiver performance in a communication system. The SINR is defined as the quotient of the signal power divided by the power of noise and interference.
The estimation of the signal power is well known and relatively simple to determine. Conventionally, a received signal strength indicator (RSSI) is measured and used as an estimate of the signal power. Such an estimate can be quite accurate especially when the interference/noise power is relatively low, i.e., in a communication environment with high SINR. However, it is more difficult to accurately estimate the interference/noise power in such an environment because the weak noise and interference energy is “buried” in the strong signal.
One approach to estimate the interference/noise power in such an environment is to stop the transmission of the signal so the received signal strength measured in such a condition will represent the power of the noise and interference. However, such an approach may not be appropriate for some applications. First of all, during the disruption of transmission, no useful information is transmitted by the transmitter and this reduces the channel's utilization. Moreover, in some communication systems, e.g., an OFDM multimedia broadcasting system, stopping or cycling transmissions from high power transmitters may damage equipment and is not recommended.
Therefore, it would be desirable to have a system that operates to accurately determine an interference and noise estimate at a receiving device in a communication network without disrupting normal network operations, thereby allowing a SINR to be determined so that the performance of the network can be determined and/or optimized.